Cooling structure of solid state and formation thereof with integrated package

ABSTRACT

A cooling structure of solid state applied to a heat source has a module of thermoelectric transfer and a module of thermo transfer including two structures of passive cooling connected and attached the module of thermoelectric transfer, respectively. One structure of first structure of passive cooling is near heat source and heat generated by the heat source is transferred to another structure of passive cooling through the one structure passive cooling and the module of thermoelectric transfer when electrical power is employed to the module of thermoelectric transfer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to the cooling structure of solid state, the formation and application thereof. More specifically, this invention relates to the cooling structure of solid state in combination the structures of active and passive cooling, the formation and application thereof.

2. Description of the Prior Art

With the development of high integrality for electric products, the issue about heat dissipation from CPU, LD or power transistor becomes more and more important. Cooling device of solid state is mostly used because of its high cooling power and low cooling temperature.

Generally, the cooling modules for the cooling device of solid state include the types of passive cooling and active cooling. A heat sink, with passive cooling, dissipates heat when itself is in temperature higher than an environment. Oppositely, a thermoelectric cooler, with active cooling, dissipates heat even the temperature itself is lower than the environment. The structure of thermoelectric cooler is advantageous without pollution and noise, and with compact and light volume.

For example, the known system of heat dissipation for the package structure of IC has thermoelectric device with predetermined size and shape associated with heat sink. However, on consideration of the variety of the package structures of IC, the end product of thermoelectric device restricts the selectivity for heat sink. Furthermore, the easy assembly and use for the dissipation elements would be considered for selecting the system of heat dissipation. For example, the mechanical intensities of conventional thermoelectric material are susceptible to crack and break when attached or used. Furthermore, the interfaces of hereto materials among the thermoelectric material, heat sink and package structure of IC leading to much thermal resistance. Once the existence of the more and more interfaces of hereto materials, the dissipation effect could be down. Furthermore, the done thermoelectric device and heat sink assembled to the package structure of IC increase the volume of a whole package.

SUMMARY OF THE INVENTION

To resolve the issue of heat dissipation caused by the interface of hereto materials, the structure of solid state in combination structures of active and passive cooling is provided herein. The structure of active cooling is directly formed or combined on the one of passive cooling during the formation of the structure of passive cooling to reduce the formation of hereto surface that causes the poor heat dissipation and transference.

To reduce the size of an electrical device on consideration of heat dissipation, the structure of solid state in combination of active and passive cooling is provided herein. The cooling structure is directly applied to single electronics device, such as the package structure of IC, without the addition of assembly or fixture.

Accordingly, a cooling structure of solid state applied to a heat source has a module of thermoelectric transfer and a module of thermal transfer including a first structure of passive cooling and a second structure of passive cooling connected and attached the module of thermoelectric transfer, respectively. The structure of first structure of passive cooling is near heat source and heat generated by the heat source is transferred to the structure of second structure of passive cooling through the structure of first structure of passive cooling and the module of thermoelectric transfer when electrical power is employed to the module of thermoelectric transfer.

Accordingly, a method of forming cooling structure of solid state is provided. A plurality of first adhesion structures are on the first surface of a first structure of passive cooling. A plurality of thermoelectric transfer structures are positioned on the first surface. Each plurality of thermoelectric transfer structures is associated with each of the first adhesion structures. A plurality of second adhesion structures are on the second surface of a second structure of passive cooling. Each the plurality of thermoelectric transfer structures is attached to each of the second adhesion structures.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the present invention will become more fully apparent from the following detailed description when read in conjunction with the accompanying drawings with like reference numerals indicating corresponding parts throughout, wherein:

FIG. 1 is a schematically side diagram illustrating a structure of active cooling in accordance with one embodiment of the present invention.

FIG. 2 is a side-sectional diagram illustrating a cooling structure of solid state in accordance with one embodiment of the present invention.

FIG. 3A is a cross-sectional diagram illustrating a cooling structure of solid state applied to a package of wire bond in accordance with the present invention.

FIG. 3B is a cross-sectional diagram illustrating a cooling structure of solid state applied to a package of cavity-down in accordance with the present invention.

FIG. 3C is a cross-sectional diagram illustrating a cooling structure of solid state applied to a lead-frame package in accordance with the present invention.

FIG. 3D is a cross-sectional diagram illustrating a cooling structure of solid state applied to multi-chip package in accordance with the present invention.

FIG. 4A to FIG. 4D is a cross-sectional diagrams illustrating a cooling structure of solid state integrated to a package structure of wire bond in accordance with the present invention.

FIG. 5A to FIG. 5D are schematically cross-sectional diagrams illustrating an exemplary cooling structure of solid state integrated into a package structure of wire bond in accordance with the present.

FIG. 6 is a schematically cross-sectional diagram illustrating the cooling structure combined with a molding frame in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference is now made in detail to specific embodiments of the present invention that illustrate the best mode presently contemplated by the inventors for practicing the invention. It should be understood that the description of the best mode is merely illustrative and that it should not be taken in a limiting sense.

FIG. 1 is a schematically side diagram illustrating a structure of active cooling in accordance with one embodiment of the present invention. For simplification, the structure of active cooling 10 is repeatedly shown in the following drawings without detail. In fact, the structures of active cooling 10 in other drawings are identical to the one in FIG. 1.

Referring to FIG. 1, the structure of active cooling 10, such as a module of thermoelectric transfer, mainly includes thermoelectric elements 11 a, 11 b, and conductive junction 12 on the ends of the thermoelectric elements 11 a, 11 b. The conductive junction 12 a is on the end of the thermoelectric element 11 a, as well as the conductive junction 12 b on the end of the thermoelectric element 11 b. The conductive junctions 12 a and 12 b are on the same side but not connected with each other. The conductive junction 12 is positioned on the other end of the thermoelectric element 11 a and parallel to thermoelectric element 11 b. In one embodiment, on one hand the conductive junctions 12 a and 12 b connect with an exterior electrical power output or electrical power input 14, and on the other hand each conductive junction 12 a or 12 b connects with one end of the thermoelectric element 11 b or thermoelectric element 11 a of the other structure of active cooling 10. That is, the two structure of active cooling 10 neighbor each other share the conductive junction 12 a or 12 b. Furthermore, the conductive junction 12, conductive junction 12 a or 12 b is substantially vertical to the thermoelectric elements 11 a and 11 b.

In one embodiment, each thermoelectric elements 11 a and 11 b constitute a pair of thermoelectric couple, and are made of the materials with the different conductivities. For example, but not limited to, on one hand the thermoelectric element 11 a is made of P-type semiconductor material of bismuth/telluric alloy for providing electrical holes, and on the other hand the thermoelectric element 11 b is made of N-type semiconductor material of bismuth/telluric alloy for providing electrons. Furthermore, the conductive junctions 12 a, 12 b and conductive junction 12, such as consisted of a layer of conductive connection 8 and an adhesive layer of solder paste 9, is used as the electrodes of the thermoelectric elements 11 a and 11 b, is attached to the thermoelectric elements 11 a and 11 b. With the connection of the conductive junctions 12 a, 12 b and conductive junction 12, the thermoelectric elements 11 a and 11 b are electrical in series but thermal in parallel.

FIG. 2 is a side-sectional diagram illustrating a cooling structure of solid state in accordance with one embodiment of the present invention. A cooling structure of solid state 20 includes a module of thermal transfer, such as two structures of passive cooling 22 a and 22 b in parallel and one or more structures of active cooling 10 is positioned between the structures of passive cooling 22 a and 22 b. The parts of structures of passive cooling 22 a and 22 b near the structure of active cooling 10 support the structure of active cooling 10 and are electrically insulating from the structure of active cooling 10. In the embodiment, the structures of passive cooling 22 a and 22 b are made of the materials with both good thermal and electrical conductivities, such as copper or aluminum metal or alloy. Furthermore, the interface between the structure of passive cooling 22 a or 22 b and the structure of active cooling 10 would be processed to be electrically insulating. Different from a conventional cooling device of solid state with a ceramic substrate, one of features of the present invention provides the structure of active cooling 10 in combination of the structures of passive cooling 22 a and 22 b, which reduces thermo resistance because of a hetero-interface. Moreover, the structures of passive cooling 22 a and 22 b is made of metal, alloy or semiconductor based materials, are with the thermal conductivities better than the conventional ceramic substrate, so as to improve heat dissipation.

It is noted that a layer of electrical insulation is just used for insulation rather than supporting even though the layer of electrical insulation is formed by processing the interface between the structure of passive cooling 22 a or 22 b and the structure of active cooling 10, so the thermal resistance for the layer of electrical insulation with the minute thickness would be neglected.

In the embodiment, the structure of passive cooling 22 a, such as a plurality of fins 23 in parallel, are isolated from each another but connected with a backplate 24. One side of the structure of passive cooling 22 a are attached to the structure of active cooling 10 and used for a heat sink, extract heat from the structure of active cooling 10 and drain the heat out of the other side of the structure of passive cooling 22 a. Furthermore, the heat fins 23 would be with any suitable shape, such as plate, column or cube. Moreover, the pitch between any neighbor two heat fins 23, the amount and length are adjustable.

Next, the structure of passive cooling 22 b, such as a heat spreader, has one side attached and connected to the structure of active cooling 10, and the other side near a heat source for receiving heat generated from the heat source and transferring the heat to the structure of active cooling 10. Similar to the structure of passive cooling 22 a, the structure of passive cooling 22 b would be with any suitable shape, such as plate, column or cube. Moreover, the pitch between any neighbor two heat fins 23, the amount and length are adjustable. In accordance with the present invention, the cooling structure of solid state 20, which has the structures of passive cooling 22 a and 22 b in combination of the structure of active cooling 10 with any amount, size, and configuration, are variable for any requirement, especially for a package design. Thus, different from a conventional package with a post-formed additional heat device, in the embodiment of the present invention, a thermoelectric module is directly formed under the heat fins, rather than the addition of thermoelectric materials both on a device and under the heat fins. Such a structure would dissipate rapidly the heat from a chip, reduce both thermal resistance and volume and provides a design of heat dissipation with low cost and little complexity.

FIG. 3A to FIG. 3D are cross-sectional diagrams illustrating a cooling structure of solid state applied to a conventional package structure. It is noted that the exemplary package structure is applied to not only the following type but also a dual in-line package (DIP), flat package (FP), pin grid array (PGA) or ball grid array (BGA). Especially, the embodiment illustrated with a single chip is also applied to other packages of stack-chip or multichip sets.

FIG. 3A is a cross-sectional diagram illustrating a cooling structure of solid state applied to a package of wire bond in accordance with the present invention. The heat source 30, such as a chip in operation, is attached on a print circuit board 32 and connected to one bonding pad (not shown) on the surface of the print circuit board 32 with conductive wires 35, so as to electrically connect with the heat source 30 and the print circuit board 32. The print circuit board 32 also includes other conductive structures 33, such as solder balls, positioned on the other surface of the print circuit board 32 for the electrical connection with an exterior device. The exemplary cooling structure of solid state 20 is overlaid on the heat source 30. With any suitable method, such as molding compound is overlaid on the structure of passive cooling 22 b of the cooling structure of solid state 20 for attaching the cooling structure of solid state 20. Such as a cooling structure of solid state 20 applied to a package structure of wire bond is beneficial for the design of heat sink for the whole package structure.

FIG. 3B is a cross-sectional diagram illustrating a cooling structure of solid state applied to a package of cavity-down in accordance with the present invention. The print circuit board 32 is with a cavity for positioning the heat source 30 that is connected to one bonding pad (not shown) on the surface of the print circuit board 32 with conductive wires 35 for electrically connecting with the heat source 30 and print circuit board 32. The cavity is full of the molding compound 34 that also covers the heat source 30 and the conductive structures 33. The print circuit board 32 also includes other conductive structures 33 positioned on the other surface of the print circuit board 32 for the electrical connection with an exterior device. With any suitable method, such as an adhesion layer is attached to the other surface of the print circuit board 32 for attaching the heat source 30. Such as a cooling structure of solid state 20 applied to a package structure of cavity down is beneficial for the design of heat sink for the whole package structure.

FIG. 3C is a cross-sectional diagram illustrating a cooling structure of solid state applied to a lead-frame package in accordance with the present invention. The heat source 30 is attached on the structure of passive cooling 22 b of the 20 a with an adhesive layer of thermal-conductive insulation. The inner leads 36 of a lead-frame are connected to the bonding pads (not shown) on the surface of the heat source 30 with the conductive wires 35, so as to electrically connect with the heat source 30 and the lead-frame. The molding compound 34 encapsulates the heat source 30, the conductive structures 33, the partial conductive wires 35 and around the structure of passive cooling 22 b. Such as a cooling structure of solid state 20 applied to a package structure of lead-frame is beneficial for the design of heat sink for the whole package structure.

FIG. 3D is a cross-sectional diagram illustrating a cooling structure of solid state applied to multi-chip package in accordance with the present invention. The package structures of lead-frame in FIG. 3 are attached on the print circuit board 32 with soldering. Furthermore, the size of the structure of passive cooling 22 a of the cooling structure of solid state 20 would cover a plurality of package structures of lead-frame and be extended to the print circuit board 32. Such as a cooling structure of solid state 20 applied to a multi-chip package is beneficial for the design of heat sink for the whole package structure.

Accordingly, the exemplary cooling structure of solid state 20 would be integrated into the heat sink of a package structure and applied to single chip, multi-chip or a wafer, as well as a wafer-level package. It is understandable that the structure of passive cooling 22 a, 22 b of the cooling structure of solid state 20 and the structure of active cooling 10 would have variable shapes, sizes, and numbers for a desired requirement. Thus, the issue of conventional hot spots would be resolved by the compact structure of the present invention.

FIG. 4A to FIG. 4D is a cross-sectional diagram that illustrating a cooling structure of solid state integrated to a package structure of wire bond. It is noted that the exemplary package structure herein would be integrated into any type of package. Moreover, the exemplary single chip integrated with the cooling structure of solid state would be in the process of packaging single chip or un-sawed chips in the wafer-level structure. Furthermore, the circuit related to control an active cooling structure is not shown herein without limitation of the claimed scope.

Referring to FIG. 4A, a substrate 40 is provided for subsequently forming the heat fin 23 and backplate 24. In one embodiment, the substrate 40 is made of the materials with good thermo-conductivity, such as metal copper, aluminum, or copper, aluminum or silicon alloy, and has two surface 40 a and 40 b facing with each other. Furthermore, the substrate 40 is with the available shape or size, such as a circle similar to the size of a wafer or square similar to the size of a chip. Next, an insulation film 45 and a layer of inter connection (not shown) such as a metallic layer is subsequently formed on the surface 40 a of the substrate 40. The portion of the layer of inter connection is removed to form a plurality structure of interconnection 42 position the surface 40 a. With any suitable method, such as screen printing, a solder paste 44 is positioned on each the structure of interconnection 42 for sequential adhesion. It is noted that such a conductive junction 12 (or 12 a, 12 b) consists of the structure of interconnection 42 and the solder paste 44. In other embodiment, on the surface 40 a, the portion of the substrate 40 is removed with lithography and etching to form a plurality of heat fins 23. The heat fins 23 are configured for not only heat dissipation but also attachment, as well as the structure of passive cooling 22 a in FIG. 3D.

Furthermore, the insulation film 45 is implemented by sintering. Alternatively, the insulation film 45 is formed by electroplating. The thermo resistance would be neglect because of the thin thickness of the insulation film 45.

Referring to FIG. 4B, on the other surface 40 b of the substrate 40, the portion of the substrate 40 is removed with lithography and etching, such as micro electromechanical processing, semiconductor processing or precision machine processing, to form a plurality of isolated heat fin 23. The residual substrate 40 at the bottom connecting the heat fins 23 is the backplate 24. Furthermore, with any suitable method, such as sputtering, evaporation or electroplating, the components thermoelectric elements 11 a and 11 b of the structure of active cooling 10 are positioned on the 44. Moreover, the arrangement of the structure of active cooling 10 on the backplate 24 would be interlacing, facing, or other types. Next, the structure 25 of the cooling structure of solid state 20 is attached with the solder paste 44.

Next, referring to FIG. 4C, a package structure 50 includes an attached structure of passive cooling 22 b. Similar to FIG. 4A, an insulation layer 51 and a layer of interconnection (not shown), such as a metallic layer, are sequentially formed on one surface 46 a of the structure of passive cooling 22 b. The portion of the layer of inter connection is removed to form a plurality structure of interconnection 47 position the surface 46 a. With any suitable method, such as printing, a solder paste 49 is positioned on each the structure of interconnection 47. Furthermore, the structures of interconnection 47 are substantially on the heat source 30 for the path reduction of heat flow.

Referring to FIG. 4D includes the package structure 50 of FIG. 4C and the structure 25 of FIG. 4B. The structure of active cooling 10 in the structure 25 is positioned on the solder paste 49 of the package structure 50, such as with flip chip technology. It is understandable that a plurality of conductive structures 33 are positioned, with any suitable method such as bumping, on the other surface of the print circuit board 32, and then reflowed to connect with the package structure 50 and the structure 25. Accordingly, during the manufacture of the cooling structure of solid state, some components are first integrated into a precedent package structure and then attached to other components. It is not necessary for such a cooling structure of solid state to attach a device with a conventional mechanical method or other device, so the problems on thermo resistance and hot spot would be reduced or avoided.

In addition of the formation of package device with the cooling structure, the exemplary embodiment according to the present invention is implemented by forming the cooling structure of solid state followed by the integration with the package structure. FIG. 5A to FIG. 5D are schematically cross-sectional diagrams illustrating an exemplary cooling structure of solid state integrated into a package structure of wire bond in accordance with the present. Different from the precedent embodiment, referring to FIG. 5A, the structure of active cooling 10 of this embodiment is positioned to the structure of passive cooling 22 b in the package structure but not integrated. Similarly, an insulation layer 51, the structure of interconnection 47 and solder paste 49 constituted the conductive junction 12, 12 a or 12 b are formed on the surface 46 a of the structure of passive cooling 22 b. Next, the components of the structure of active cooling 10 are positioned on the solder paste 49 with any suitable methods and then reflowed. Furthermore, the structure of passive cooling 22 b would be combined with a molding compound 52 first and then used in the assignment of the structure of active cooling 10, such as FIG. 6.

Referring to FIG. 5B, the manufacture of the structure of passive cooling 22 a is similar to the precedent embodiment, but without the assignment of the structure of active cooling 10 on the 44. Next, the components of FIG. 5A and FIG. 5B are assembled with reflowing and then integrated with the heat source 30 on the print circuit board 32, shown in FIG. 5C. Next, the cooling structure of solid state is adhered and attached to the print circuit board 32 with the molding compound 34, shown as FIG. 5D.

When there has been illustrated and described what is at present invention considered to be a preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made, and equivalents may be substituted for elements thereof without departing from the true scope of the invention. In addition, may modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the true scope thereof. Therefore, it is intended that this invention not be limited to template for carrying out the invention, but that the invention will include all embodiments falling within the scope of the appended claims. 

1. A cooling structure of solid state, applied to a heat source, said cooling structure of solid state comprising: a module of thermoelectric transfer; and a module of thermal transfer including a first structure of passive cooling and a second structure of passive cooling connected and attached said module of thermoelectric transfer, respectively, said first structure of passive cooling near said heat source; wherein heat generated by said heat source is transferred to said second structure of passive cooling through said first structure of passive cooling and said module of thermoelectric transfer when electric power is employed to said module of thermoelectric transfer.
 2. The cooling structure of solid state according to claim 1, wherein said module of thermoelectric transfer comprises a plurality of thermoelectric elements and conductive junctions, a portion of said conductive junctions configured for connecting any two said thermoelectric elements neighboring each other and said heat source.
 3. The cooling structure of solid state according to claim 2, wherein said plurality of thermoelectric elements are made of N-type and P-type semiconductor materials.
 4. The cooling structure of solid state according to claim 1, wherein said first structure of passive cooling comprises a part of thermal conduction and a part of electro insulation between said module of thermoelectric transfer and said part of thermal conduction.
 5. The cooling structure of solid state according to claim 4, wherein said part of electro insulation is implemented by electroplating, coating, sputtering or sintering. a ceramic material, oxide layer or electrical insulator.
 6. The cooling structure of solid state according to claim 1, wherein said second structure of passive cooling comprises a part of thermal conduction and a part of electrical insulation between said module of thermoelectric transfer and said part of thermal conduction.
 7. The cooling structure of solid state according to claim 6, wherein said part of electro insulation is implemented by electro-plating, coating, sputtering or sintering a ceramic material, oxide layer or electrical insulator.
 8. A package system of integrating package and cooling structure, comprising: a package module including a heat source; a module of thermoelectric transfer; and a module of thermal transfer including a first structure of passive cooling and a second structure of passive cooling connected and attached said module of thermoelectric transfer, respectively, said first structure of passive cooling near said heat source; wherein heat generated by said heat source is transferred to said second structure of passive cooling through said first structure of passive cooling and said module of thermoelectric transfer when electrical power is employed to said module of thermoelectric transfer.
 9. The package system of integrating package and cooling structure according to claim 8, wherein said package module further comprises an electric circuit board, a plurality of conductive junctions and a molding compound, said heat source on a surface of said printed circuit board, said plurality of conductive junctions electrically connecting said electric circuit board and said heat source, and said molding compound on a portion of said surface, said heat source and said plurality of conductive junctions.
 10. The package system of integrating package and cooling structure according to claim 8, wherein said package module further comprises a lead-frame, a plurality of structures of conductive connection and a molding compound, said plurality of structure of conductive connection electrically connecting a plurality of inner leads of said lead-frame and said heat source, said molding compound encapsulating said plurality of inner leads, said heat source and said plurality of structures of conductive connection.
 11. The package system of integrating package and cooling structure according to claim 8, wherein said module of thermoelectric transfer comprises a plurality of thermoelectric elements and conductive junctions, a portion of said conductive junctions configured for connecting any two said thermoelectric elements neighboring each other and said heat source.
 12. The package system of integrating package and cooling structure according to claim 8, wherein said first structure of passive cooling is a metallic heat sink with a sintered surface near said module of thermoelectric transfer.
 13. The package system of integrating package and cooling structure according to claim 8, wherein said second structure of passive cooling comprises a part of thermal conduction and a part of electrical insulation between said module of thermoelectric transfer and said part of thermal conduction.
 14. The package system of integrating package and cooling structure according to claim 8, wherein said second structure of passive cooling comprises a metallic substrate, said metallic substrate with a sintered surface near said module of thermoelectric transfer on one side and a plurality of metallic heat fins on the other side.
 15. A method of forming cooling structure of solid state, comprising: providing a first structure of passive cooling and a plurality of first adhesion structure on a first surface of said first structure of passive cooling; positioning a plurality of structure of thermoelectric transfer on said first surface, wherein each of said structures of thermoelectric transfer is associated with each of said first adhesion structures; providing a second structure of passive cooling and a plurality of second adhesion structure on a second surface of said second structure of passive cooling; and attaching each of said structures of thermoelectric transfer to each of said second adhesion structures.
 16. The method of forming cooling structure of solid state according to claim 15, wherein the step of providing said first structure of passive cooling comprises: providing a thermal conductive substrate providing said first surface; forming a plurality of metallic structure positioned on said first surface; and forming a conductive bump on each of said metallic structures, wherein each of said first adhesion structures comprises said conductive bump and said associated metallic structure.
 17. The method of forming cooling structure of solid state according to claim 16, wherein the step of forming said conductive bump is implemented by printing.
 18. The method of forming cooling structure of solid state according to claim 15, wherein the step of positioning comprises: forming a plurality of first conductive junctions on said first surface; forming a plurality of thermoelectric elements on said plurality of first conductive junctions; and forming a plurality of second conductive junctions on said plurality of thermoelectric elements, wherein any two said thermoelectric elements neighboring each other connect through one of any said first conductive junction and any said second conductive junction.
 19. The method of forming cooling structure of solid state according to claim 15, wherein the step of said second structure of passive cooling comprises: providing a thermal conductive substrate providing said second surface; forming a plurality of metallic structure positioned on said second surface; and forming a conductive bump on each of said metallic structures, wherein each of said second adhesion structures comprises said conductive bump and said associated metallic structure.
 20. The method of forming cooling structure of solid state according to claim 19, further comprising sintering said second surface. 